An energy-saving membrane-integrated nanopowder washing and purification zero-emission process

Abstract

The invention discloses an energy-saving membrane-integrated nano powder washing and purification zero-emission process, comprising the steps of: transferring the slurry after the reaction of the reactor to a cleaning circulation tank, discharging the reactor cleaning wastewater to a sedimentation tank; transferring the cleaned slurry in the cleaning circulation tank to a concentrated slurry tank; sending the cleaned nano powder concentrated slurry to a spray dryer for drying or using a plate-frame filter press at a pressure of 0.3-0.8 MPa to filter into a filter cake, drying, sintering and crushing, and packaging the finished product; a ceramic flat membrane device is provided in the upper part of the sedimentation tank, and the sedimentation tank contains cleaning wastewater, which is filtered by the ceramic flat membrane and sent to a cleaning wastewater tank; the wastewater in the cleaning wastewater tank is treated by a primary RO membrane device, and the prepared pure water is sent to a pure water tank, and the concentrated water is sent to a secondary RO membrane device. The invention has high automation, low cost, low labor intensity, low water consumption for cleaning, high yield of nano powder, good powder dispersion performance, and powder purity of more than 99.99%.

Description

Technical Field

[0001] The invention relates to an energy-saving membrane-integrated nanometer powder washing and purification zero-emission process, belonging to the technical field of nanometer powder materials. Background Art

[0002] In the process of producing nano powder by wet chemical method, there are many kinds of anionic and cationic impurity ions left after chemical reaction. If they are not cleaned up, it will affect the performance of ultrafine (nano) powder. In addition, nano powder particles have small particle size, large specific surface area, strong surface physical and chemical action, and strong tendency to agglomerate. When such powder is washed by traditional plate and frame filtration, high-speed centrifugation and other washing methods, various filtration technologies with filter cloth as filter medium have poor particle filtration and retention performance for nano powder (particle size is nanometer level) due to the restriction of filter medium. During washing, powder is easy to be exposed from filter cloth, causing material leakage, serious product loss, and a large amount of powder is also present in the cleaning wastewater of equipment. These wastewaters containing powder are suspended in the wastewater pool of the factory and are not easy to settle. The filtrate is turbid and unclear. If it is not collected, it will cause pollution to the surrounding environment. At the same time, the slurry before washing has strong acidity and alkalinity. Each washing and purification of a batch of nano powders normally requires more than 6 times the amount of pure water. If these washing waters are not treated, it will inevitably cause environmental pollution and expensive nano powder loss.

[0003] At present, tubular ceramic ultrafiltration membranes are mainly used for cleaning and purification in China. However, this process uses a cross-flow filtration mode, which requires large equipment investment and high energy consumption. The channels in the ceramic membrane used are small, generally 4 to 6 mm. When cleaning nanopowders, the solid content can only be operated at 10 to 20%, and the channels will be blocked when the solid content is high. At the same time, it cannot solve the problem of recycling powder-containing wastewater generated by plate and frame filter pressing and equipment cleaning. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides an energy-saving membrane-integrated nano-powder washing and purification zero-emission process.

[0005] In order to achieve the above object, the present invention adopts an energy-saving membrane-integrated nano-powder washing and purification zero-emission process, which comprises the following steps:

[0006] S1. The slurry after the reaction in the reactor is transferred to the cleaning circulation tank, and the reactor cleaning wastewater is discharged to the sedimentation tank;

[0007] S2. The slurry is heated to 30-90° C. in the cleaning circulation tank, and the slurry in the cleaning circulation tank is concentrated to a solid content of 30-40% by a rotating ceramic membrane device. Then, concentrated water from the sedimentation tank and evaporation condensed water are added to the cleaning circulation tank in sequence for the first and second washings. Pure water is then continuously added to the cleaning circulation tank from the pure water tank to maintain the slurry water temperature at 30-90° C. and the solid content at 30-40%. The cleaning is continued, and the filtered wastewater containing impurity ions is sent to the cleaning wastewater tank. When the conductivity in the slurry reaches the set requirement, the addition of pure water is stopped, the rotating ceramic membrane device is stopped, and the cleaned slurry in the cleaning circulation tank is transferred to the concentrated slurry tank;

[0008] S3, the washed nano powder concentrated slurry is sent to the spray dryer for drying or the plate and frame filter press is used for filtering at a pressure of 0.3-0.8 MPa to form a filter cake, which is then dried, sintered and crushed, and the finished product is packaged. The wastewater from the plate and frame filter press is discharged into the sedimentation tank;

[0009] S4. A ceramic flat membrane device is installed in the upper part of the sedimentation tank. The sedimentation tank contains cleaning wastewater, which is filtered through the ceramic flat membrane and sent to the cleaning wastewater tank. When each batch of production slurry is transferred to the slurry concentration tank and begins to be concentrated, the high-content powder wastewater in the sedimentation tank is transferred to the cleaning circulation tank through the water pump installed at the bottom of the sedimentation tank;

[0010] S5. The wastewater in the cleaning wastewater tank is treated by the primary RO membrane device, and the prepared pure water is sent to the pure water tank, and the concentrated water is sent to the secondary RO membrane device. The pure water prepared by the two-stage RO membrane device is sent to the pure water tank, and the concentrated water is evaporated and dried into solid salt by the concentrated brine evaporation device. The distilled water of the evaporation device is sent to the cleaning circulation tank as the first or second cleaning water for the produced powder slurry.

[0011] Preferably, the cleaning wastewater generated by the cleaning circulation tank, the rotating ceramic membrane device, the concentrated slurry tank and the plate and frame filter press is collected and discharged into the sedimentation tank through a sealed pipeline.

[0012] Preferably, the rotating ceramic membrane device sets the conductivity of the cleaned nano-powder slurry according to the purity requirement of the nano-powder, and stops cleaning when the set conductivity is reached.

[0013] Preferably, the rotating ceramic membrane device uses a circular ceramic membrane with a diameter of 150-400 mm and a thickness of 5-10 mm, a central axis hole of 20-50 mm, a membrane pore size of 1-200 nm, and an operating pressure of 0.1-0.3 MPa.

[0014] Preferably, the rotating ceramic membrane device has a backwashing function, and uses compressed air with a pressure of 0.1 to 0.3 MPa to compress the filtered cleaning wastewater and backwash it from the membrane permeation side for 3 to 10 seconds.

[0015] Preferably, the rotating ceramic diaphragm of the rotating ceramic membrane device is installed on a hollow shaft, the rotating motor is frequency-controlled to rotate at 300-1000 r / min, and evenly distributed baffles are provided in the membrane shell.

[0016] Preferably, the ceramic flat membrane device uses several templates with an outer size of 250×1000 mm and a thickness of 3-10 mm, a membrane pore size of 1-200 nm, and the membrane plates are centrally arranged on a frame, under which an aeration device is provided.

[0017] Preferably, the ceramic flat membrane device adopts a suction working mode, clean water is pumped out from the center hole of the flat membrane and sent to the cleaning waste water tank, and the suction pressure is -0.01 to -0.05 MPa.

[0018] Preferably, the ceramic flat membrane device has a backwashing function, and is backwashed once every 30 to 60 minutes according to the membrane fouling condition.

[0019] Preferably, the washing wastewater overflows into the sedimentation tank after primary sedimentation in the primary sedimentation tank. A ceramic flat membrane and an aeration device are arranged in the sedimentation tank. The sedimentation tank is provided with a concentrate pump. The pump inlet is respectively connected to the primary sedimentation tank and the sedimentation tank, and the outlet is respectively connected to the primary sedimentation tank and the cleaning circulation tank.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention adopts a rotating ceramic membrane device to filter at a high speed of 300-1000r / min at 0.1-0.3MPa. The equipment investment is small and the operating cost is low. The high speed and high shear force of the equipment operation make it difficult to form a filter cake layer on the membrane surface. The membrane flux is stable and the filtration efficiency is high. The high-speed water flow shear force generated can keep the nano powder highly dispersed, the membrane separation accuracy is high, there is no powder loss during cleaning, the powder slurry can be concentrated to a solid content of 30-40%, the amount of pure water used during cleaning is reduced, and the powder purity can reach more than 99.99%.

[0022] 2. A ceramic flat membrane device is used to treat cleaning wastewater and plate and frame filter press water containing nanopowders. The device is placed in the upper middle part of the sedimentation tank and works in a negative pressure suction mode of -0.01 to -0.05 MPa. The equipment occupies a small area, has low investment and low operating costs. After the lost powder is enriched in the sedimentation tank, it is used as the first washing water for the powder slurry and pumped into the cleaning circulation tank. While washing, valuable nanopowders are recovered, which improves the product yield and reduces the amount of water used for washing the powder slurry.

[0023] 3. In the process, the cleaning wastewater is treated into pure water by two-stage reverse osmosis membrane for nano powder cleaning, realizing wastewater recycling. Two-stage reverse osmosis can recover 90-96% of water for reuse, and 4-10% of concentrated brine is evaporated into solid salt. Except for adding a small amount of tap water in the first-stage reverse osmosis device, there is no external drainage in the whole process, which saves water resources, realizes zero wastewater discharge, and solves the environmental protection problems in the production of nano powders. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0025] Figure 2 It is a schematic diagram of the washing and purification process of the rotating ceramic membrane device of the present invention;

[0026] Figure 3 This is a schematic diagram of the wastewater recovery process of the ceramic flat membrane device of the present invention;

[0027] Figure 4 It is a structural schematic diagram of the rotating ceramic membrane device of the present invention;

[0028] In the figure: 1. Reactor, 2. Cleaning circulation tank, 3. Pure water tank, 4. Secondary RO membrane device, 5. Primary RO membrane device, 6. Cleaning wastewater tank, 7. Rotating ceramic membrane device, 7.1. Upper cover, 7.2. Upper machine seal, 7.3. Cylinder, 7.4. Baffle, 7.5. Hollow shaft, 7.6. Membrane partition plate, 7.7. Ceramic rotating diaphragm, 7.8. Feed equalizing plate, 7.9. Lower cover, 7.10. Lower machine seal, 7.11. Hollow reducer, 7.12. High-speed rotary joint, 7.13. Device frame, 8. Concentrated slurry tank, 9. Ceramic flat membrane device, 10. Sedimentation tank, 11. Plate and frame filter press, 12. Cleaning circulation pump, 13. Self-priming pump, 14. Backwashing pump, 15. Concentrated water pump, 16. Backwashing buffer tank, 17. Primary sedimentation tank. DETAILED DESCRIPTION

[0029] The following embodiments are further descriptions of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0030] like Figure 1 As shown, an energy-saving membrane-integrated nanopowder washing and purification zero-emission process comprises the following steps:

[0031] S1, the slurry after the reaction in reactor 1 is transferred to the cleaning circulation tank 2, and the cleaning wastewater generated by reactor 1 is discharged to the sedimentation tank 10;

[0032] S2, heating the slurry in the cleaning circulation tank 2 to 30-90°C, and concentrating the slurry in the cleaning circulation tank 2 to a solid content of 30-40% by using a rotating ceramic membrane device 7, and then sequentially adding concentrated water from the sedimentation tank and evaporation condensed water to the cleaning circulation tank 2 for the first and second washings, and then continuously adding pure water from the pure water tank 3 to the cleaning circulation tank 2, maintaining the slurry water temperature at 30-90°C and the solid content at 30-40%, and continuously washing, and the impurity ion wastewater filtered by the cleaning is sent to the cleaning wastewater tank 6 through the backwash buffer tank 16, and when the conductivity in the slurry reaches the set requirement, stop adding pure water, stop rotating the ceramic membrane device 7, and transfer the cleaned slurry in the cleaning circulation tank 2 to the concentrated slurry tank 8;

[0033] S3, the washed nano powder concentrated slurry is sent to a spray dryer for drying or is filtered into a filter cake by a plate and frame filter press 11 at a pressure of 0.3-0.8 MPa, and then dried, sintered, and crushed. The finished product is packaged, and the wastewater from the plate and frame filter press is discharged into a sedimentation tank 10;

[0034] S4, a ceramic flat membrane device 9 is provided in the middle and upper part of the sedimentation tank 10. The cleaning wastewater containing a small amount of lost powder in the sedimentation tank 10 is filtered by the ceramic flat membrane device 9 and sent to the cleaning wastewater tank 6. The wastewater accumulates in the sedimentation tank 10 over time. When the content of the recovered and enriched powder in the wastewater reaches a certain concentration, when each batch of production slurry is transferred to the concentrated slurry tank 8 to start concentrating, the high-content powder wastewater in the sedimentation tank 10 is transferred to the cleaning circulation tank 2 through the concentrated water pump 15 provided at the bottom of the sedimentation tank 10, which not only recovers the lost high-value powder, but also serves as the first cleaning water for the newly produced nano powder slurry, saving production water, and also saving the subsequent wastewater treatment volume;

[0035] S5. The waste water in the cleaning waste water tank 6 is treated by the primary RO membrane device 5, and the prepared pure water is sent to the pure water tank 3, and the concentrated water is sent to the secondary RO membrane device 4. The pure water prepared by the two-stage RO membrane device treatment is sent to the pure water tank 3. The two-stage RO membrane treatment can recycle more than 90% of the washing waste water for reuse; the concentrated water is evaporated and dried into solid salt by the concentrated brine evaporation device, and the distilled water of the evaporation device is sent to the cleaning circulation tank 2 as the first or second cleaning water for the produced powder slurry, saving the amount of pure water.

[0036] As an improvement of the embodiment, the cleaning wastewater generated by the cleaning circulation tank 2, the rotating ceramic membrane device 7, the concentrated slurry tank 8 and the plate and frame filter press 11 are all discharged into the sedimentation tank 10 through a closed pipe, and are enriched and recovered after suction filtration by the ceramic flat membrane device 9. The lost powder caused by cleaning and plate and frame leakage is not contaminated and is fully recovered, thereby improving the product yield of nano powder production.

[0037] As an improvement of the embodiment, Figure 2 , Figure 4As shown, the rotating ceramic membrane device 7 includes a device frame 7.13, a cylinder 7.3 installed on the device frame 7.13 and a hollow shaft 7.5; a baffle 7.4 is installed on the inner wall of the cylinder 7.3, the hollow shaft 7.5 is vertically installed in the cylinder 7.3, an upper cover 7.1 and an upper machine seal 7.2 are installed on the top of the hollow shaft 7.5 and the cylinder 7.3, a membrane spacer 7.6 and a ceramic rotating diaphragm 7.7 are installed on the hollow shaft 7.5 located in the cylinder 7.3, a feed equalizing plate 7.8, a lower cover 7.9 and a lower machine seal 7.10 are installed on the bottom of the hollow shaft 7.5 and the cylinder 7.3, and a hollow reducer 7.11 and a high-speed rotating joint 7.12 are installed on the hollow shaft 7.5 located at the bottom of the device frame 7.13. The rotating ceramic membrane device 7 is connected to the cleaning circulation pump 12, the backwash pump 14, the cleaning water inlet (sedimentation tank water pump, sedimentation tank concentrated water solenoid valve, condensate water inlet valve, pure water solenoid valve) etc. through a slurry conductivity meter, a temperature sensor, a pressure sensor, a liquid level sensor and an electromagnetic flowmeter. The cleaning process is automatically controlled by a PLC program, and the washing and purification operation is stopped when the set slurry qualified conductivity is reached.

[0038] As a further improvement of the embodiment, the rotating ceramic membrane device 7 adopts a circular ceramic membrane with a diameter of 150-400mm and a thickness of 5-10mm, a central axis hole of 20-50mm, a membrane pore size of 1-200nm, an operating pressure of 0.1-0.3MPa, and a recoil function. Figure 3 As shown, specifically:

[0039] Backwashing is to use compressed air with a pressure of 0.1 to 0.3 MPa to compress the filtered cleaning wastewater, and use the cleaning wastewater to backwash from the membrane permeation side for 3 to 10 seconds to wash away the filter cake layer on the surface of the ceramic rotating membrane to maintain the stability of the membrane's permeation flux.

[0040] As an improvement of the embodiment, the rotating ceramic diaphragm of the rotating ceramic membrane device 7 is installed on a hollow shaft 7.5 that can rotate at high speed. The frequency conversion controls the rotating motor speed to be 300-1000r / min. At the same time, evenly distributed baffles 7.4 are provided in the membrane shell to form turbulent water flow at high speed to flush the surface of the ceramic rotating diaphragm, so that it is difficult to form a filter cake layer on the surface of the diaphragm when the nano powder is cleaned and purified, thereby maintaining the stability of the permeation flux of the membrane. At the same time, the cleaning and purification can be completed with 3-5 times the pure water of the slurry at a solid content of 30-40%, which greatly reduces the amount of water used for cleaning.

[0041] As an improvement of the embodiment, the ceramic flat membrane device 9 is arranged in the middle and upper part of the sedimentation tank 10, and mainly includes a self-priming pump 13, an aeration device, a backwash pump 14, a concentrate pump 15, etc., and adopts PLC automatic control. The flat membrane vacuum pump is connected to the sedimentation tank liquid level to automatically start and stop. The backwash pump 14 is controlled by programs such as water production flow meter, pressure sensor, and filtration time to start backwashing and keep the membrane filtration flux stable; the aeration device is used to prevent concentration polarization near the surface of the flat membrane.

[0042] As an improvement of the embodiment, the ceramic flat membrane device 9 uses a number of membranes with an outer size of 250×1000mm and a thickness of 3-10mm as needed, with evenly distributed water production holes in the center, a membrane pore size of 1-200nm, and the membrane plates are centrally arranged on the frame; the ceramic flat membrane device 9 adopts a suction working mode, and clean water is extracted from the center hole of the flat membrane and sent to the cleaning wastewater tank 6, and the suction pressure is -0.01 to -0.05MPa. The ceramic flat membrane device 9 has a recoil function, and according to the membrane pollution condition, recoil is set once every 30 to 60 minutes.

[0043] As an improvement of the embodiment, the present invention is provided with a primary sedimentation tank 17 and a sedimentation tank 10, and the washing wastewater overflows to the sedimentation tank 10 after primary sedimentation in the primary sedimentation tank 17, and the sedimentation tank 10 is provided with a ceramic flat membrane and an aeration device, and the sedimentation tank 10 is provided with a concentrate pump 15, and the inlet of the concentrate pump 15 is respectively connected to the primary sedimentation tank 17 and the sedimentation tank 10, and the outlet is respectively connected to the primary sedimentation tank 17 and the cleaning circulation tank 2. Normally, the wastewater of the sedimentation tank 10 is pumped into the primary sedimentation tank 17 by the concentrate pump 15 for pre-sedimentation, and after the powder slurry of the cleaning circulation tank 2 is fed, when concentrated, the concentrate pump 15 pumps the wastewater of the primary sedimentation tank 17 and the sedimentation tank 10 into the cleaning circulation tank 2 for the first washing, recovering the lost powder, and reducing the amount of pure water used for cleaning.

[0044] Example 1

[0045] An energy-saving membrane-integrated nanopowder washing and purification zero-emission process comprises the following steps:

[0046] S1, the slurry after the reaction in reactor 1 is transferred to the cleaning circulation tank 2, and the cleaning wastewater generated by reactor 1 is discharged to the sedimentation tank 10;

[0047] S2, heating the slurry in the cleaning circulation tank 2 to 60°C, and concentrating the slurry in the cleaning circulation tank 2 to a solid content of 30% by using a rotating ceramic membrane device 7, and then sequentially adding concentrated water from the sedimentation tank and evaporation condensed water to the cleaning circulation tank 2 for the first and second washings, and then continuously adding pure water from the pure water tank 3 to the cleaning circulation tank 2, maintaining the slurry water temperature at 60°C and the solid content at 30%, and continuously washing, and the impurity ion-containing wastewater filtered by the cleaning is sent to the cleaning wastewater tank 6 through the backwash buffer tank 16, and when the conductivity in the slurry reaches the set requirement, stop adding pure water, stop rotating the ceramic membrane device 7, and transfer the cleaned slurry in the cleaning circulation tank 2 to the concentrated slurry tank 8;

[0048] S3, the washed nano powder concentrated slurry is sent to the plate and frame filter press 11 under a pressure of 0.4MPa, filtered into a filter cake, dried, sintered and crushed, and the finished product is packaged, and the plate and frame filter press wastewater is discharged into the sedimentation tank 10;

[0049] S4, a ceramic flat membrane device 9 is provided in the middle and upper part of the sedimentation tank 10. The cleaning wastewater containing a small amount of lost powder in the sedimentation tank 10 is filtered by the ceramic flat membrane device 9 and sent to the cleaning wastewater tank 6. The wastewater accumulates in the sedimentation tank 10 over time. When the content of recovered and enriched powder in the wastewater reaches a certain concentration, when each batch of production slurry is transferred to the concentrated slurry tank 8 to start concentrating, the high-content powder wastewater in the sedimentation tank 10 is transferred to the cleaning circulation tank 2 through the concentrated water pump 15 provided at the bottom of the sedimentation tank 10;

[0050] S5. The waste water in the cleaning waste water tank 6 is treated by the primary RO membrane device 5, and the prepared pure water is sent to the pure water tank 3, and the concentrated water is sent to the secondary RO membrane device 4. The pure water prepared by the two-stage RO membrane device treatment is sent to the pure water tank 3. The two-stage RO membrane treatment can recycle more than 90% of the washing waste water for reuse; the concentrated water is evaporated and dried into solid salt by the concentrated brine evaporation device, and the distilled water of the evaporation device is sent to the cleaning circulation tank 2 as the first or second cleaning water for the produced powder slurry, saving the amount of pure water.

[0051] The invention originates from the cleaning process transformation of a zirconium oxide nano powder production enterprise. The original nano powder production is a powder slurry produced by a wet chemical method, which is washed by a plate and frame filter press. Because the filter cloth of the plate and frame filter press leaks at the beginning of filtration, the first-level cleaning of the plate and frame, the plate and frame unloading and other operations will cause about 1-5% of the nano powder to enter the wastewater pool with a large amount of acidic washing wastewater, resulting in many wastewater pools on site. However, because the nano powder particles are small and not easy to precipitate, a large amount of wastewater containing powder overflows, causing the factory area to be white. At the same time, it is also necessary to match large-scale sewage treatment facilities.

[0052] The energy-saving membrane-integrated nano powder washing and purification zero-emission process of the present invention can achieve a high yield, while improving the dispersibility and high purity of the nano powder (up to 99.99% or more). The washing wastewater is recycled to solve the environmental protection problem.

[0053] The comparison between the present invention and the traditional washing process is shown in Table 1 below:

[0054] Table 1 Comparison of washing processes

[0055]

[0056]

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An energy-saving membrane-integrated wet chemical process for producing nanopowders by washing and purifying with zero emission, characterized in that: The following steps are involved: S1. The slurry after the reaction in the reactor is transferred to the cleaning circulation tank, and the reactor cleaning wastewater is discharged to the sedimentation tank; S2. The slurry is heated to 30-90°C in the cleaning circulation tank, and the slurry in the cleaning circulation tank is concentrated to a solid content of 30-40% by a rotating ceramic membrane device. Then, the concentrated water from the sedimentation tank and the evaporation condensed water are added to the cleaning circulation tank in turn for the first and second washings. Then, pure water is continuously added to the cleaning circulation tank from the pure water tank to maintain the slurry water temperature at 30-90°C and the solid content at 30-40%. The slurry is continuously washed, and the filtered wastewater containing impurity ions is sent to the cleaning wastewater tank. When the conductivity of the slurry reaches the set requirements, the addition of pure water is stopped, the rotating ceramic membrane device is stopped, and the cleaned slurry in the cleaning circulation tank is transferred to the concentrated slurry tank; the rotating ceramic membrane device adopts a circular ceramic diaphragm with a diameter of 150-400mm and a thickness of 5-10mm, a central axis hole of 20-50mm, a membrane pore size of 1-200nm, and an operating pressure of 0. 1~0.3MPa, the rotating ceramic membrane device has a backwash function, and uses compressed air with a pressure of 0.1~0.3MPa to compress the filtered cleaning wastewater, and backwash it from the membrane permeation side for 3~10s. The rotating ceramic diaphragm of the rotating ceramic membrane device is installed on a hollow shaft, and the frequency conversion controls the rotating motor speed to be 300~1000r / min. At the same time, a uniformly distributed baffle is arranged in the membrane shell; the rotating ceramic membrane device includes a device frame, a cylinder body and a hollow shaft installed on the device frame; a baffle is installed on the inner wall of the cylinder, the hollow shaft is vertically installed in the cylinder, an upper cover and an upper machine seal are installed on the top of the hollow shaft and the cylinder body, a membrane spacer and a ceramic rotating diaphragm are installed on the hollow shaft in the cylinder body, a feed equalizing plate, a lower cover and a lower machine seal are installed on the bottom of the hollow shaft and the cylinder body, and a hollow reducer and a high-speed rotating joint are installed on the hollow shaft at the bottom of the device frame; S3, the washed nano powder concentrated slurry is sent to the spray dryer for drying or the plate and frame filter press is used for filtering at a pressure of 0.3-0.8 MPa to form a filter cake, which is then dried, sintered and crushed, and the finished product is packaged. The wastewater from the plate and frame filter press is discharged into the sedimentation tank; S4. A ceramic flat membrane device is installed in the upper part of the sedimentation tank. The sedimentation tank contains cleaning wastewater, which is filtered through the ceramic flat membrane and sent to the cleaning wastewater tank. When each batch of production slurry is transferred to the slurry concentration tank and begins to be concentrated, the high-content powder wastewater in the sedimentation tank is transferred to the cleaning circulation tank through the water pump installed at the bottom of the sedimentation tank; S5. The wastewater in the cleaning wastewater tank is treated by the primary RO membrane device, and the prepared pure water is sent to the pure water tank, and the concentrated water is sent to the secondary RO membrane device. The pure water prepared by the two-stage RO membrane device is sent to the pure water tank, and the concentrated water is evaporated and dried into solid salt by the concentrated brine evaporation device. The distilled water of the evaporation device is sent to the cleaning circulation tank as the first or second cleaning water for the produced powder slurry.

2. The energy-saving membrane-integrated wet chemical process for producing nanopowders by washing, purifying and zero-emission according to claim 1, characterized in that: The cleaning wastewater generated by the cleaning circulation tank, the rotating ceramic membrane device, the concentrated slurry tank and the plate and frame filter press is collected and discharged into the sedimentation tank through a sealed pipeline.

3. The energy-saving membrane-integrated wet chemical process for producing nanopowders by washing, purifying and zero-emission according to claim 1, characterized in that: The rotating ceramic membrane device sets the conductivity of the cleaned nano-powder slurry according to the purity requirement of the nano-powder, and stops cleaning when the set conductivity is reached.

4. The energy-saving membrane-integrated wet chemical process for producing nanopowders by washing, purifying and zero-emission according to claim 1, characterized in that: The ceramic flat membrane device adopts several templates with an outer size of 250×1000 mm and a thickness of 3-10 mm, and the membrane pore diameter is 1-200 nm. The membrane plates are centrally arranged on a frame, and an aeration device is arranged under the frame.

5. The energy-saving membrane-integrated wet chemical process for producing nano-powders by washing, purifying and zero-emission according to claim 4, characterized in that: The ceramic flat membrane device adopts a suction working mode, clean water is pumped out from the center hole of the flat membrane and sent to the cleaning waste water tank, and the suction pressure is -0.01 to -0.05 MPa.

6. The energy-saving membrane-integrated wet chemical process for producing nanopowders by washing, purifying and zero-emission according to claim 5, characterized in that: The ceramic flat membrane device has a backwashing function, and is backwashed once every 30 to 60 minutes according to the membrane fouling condition.

7. The energy-saving membrane-integrated wet chemical process for producing nano-powders by washing, purifying and zero-emission according to claim 1, characterized in that: The washing wastewater overflows into the sedimentation tank after primary sedimentation in the primary sedimentation tank. A ceramic flat membrane and an aeration device are installed in the sedimentation tank. The sedimentation tank is equipped with a concentrate pump. The pump inlet is connected to the primary sedimentation tank and the sedimentation tank respectively, and the outlet is connected to the primary sedimentation tank and the cleaning circulation tank respectively.

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